The present invention relates to a unit for the transfer and distribution of a liquid and a method of manufacturing the same according to claims 1 respectively 12. The invention further relates to a refill for a dispenser for volatile liquids.
In order to transfer liquids it is known to use capillary action which is dependent on the cohesive forces within the liquid and the adhesive forces of the liquid to a capillary medium comprising small channels, e.g. pores or spaces between fibers. Such a capillary medium, e.g. a wick, being introduced through an opening into a reservoir, can therefore be used to draw a liquid out of said reservoir passively by means of capillary action only, i.e. without additional sucking. The transferred liquid may be used to distribute chemical substances to the ambient air in order to generate or mask an odour, to evoke a medical or organoleptic effect or to affect insects.
The U.S. Pat. No. 5,114,625 discloses a fragrance dispenser with a liquid reservoir and a wick with a liquid receiving end disposed in the reservoir for drawing liquid therefrom into the wick. A portion of the wick length is exposed to an air flow provided by a fan.
However, the distribution of volatile chemical substances contained in the liquid in the air flow is not sufficiently homogenous when the air flow is brushing over the wick. Further, in most cases dispensing a substance cannot be done without generation of an external air flow in order to evaporate a given amount of liquid per unit time.
The wicks used in prior art dispensing devices are difficult to exchange as they have to be mounted in such a way that the wick is arranged in a defined position relative to the reservoir. This is rendered difficult as wicks are generally soft. Further, the reservoir including the wick has to be tight to prevent spilling of the liquid and uncontrolled evaporation. The same problem arises with a refill for such a device. A refill already including a wick has to be tightly sealed before use, while refill and wick separated from each other have to be such that the wick is easy and clean to insert and the refill is tight before and during use.
It is therefore an object of the invention to provide a unit for the transfer and distribution of a volatile liquid that has a good efficiency in evaporating liquid, is easy and cheap to manufacture and is easily and hygienically insertable into a reservoir, especially the reservoir of a refill.
It is another object of the invention to provide a method of manufacturing such an improved transfer unit.
It is a further object of the invention to provide a refill suited for the use with such a transfer unit.
The above and other objects of the invention are achieved by a transfer unit as specified in claim 1, a method of manufacturing the same as specified in claim 12, a refill and a dispenser with such a transfer unit and such a refill.
According to the invention a shaft comprising a first capillary medium to draw a liquid into the shaft due to capillary action, e.g. a wick, scrib rod or a porous rod, is provided with an integrated screen to serve as an enlarged liquid receiving area from which the liquid is easily evaporated to the ambient air. To provide an enlarged area, the screen is preferably at least two to three times as wide as the shaft. By capillary action the liquid is drawn from the shaft to the screen and distributed over it, using a second capillary medium connected to the first capillary medium. As first capillary medium in general any material capable of absorbing and transferring a liquid due to capillary action is suited, e.g. material containing natural or synthetic fibers, woven or non-woven fabrics, porous media, capillary tubes, or a rod with external grooves, e.g. as described in U.S. Pat. No. 4,913,350. As second capillary medium a material with open pores from which liquid evaporates is suited, e.g. material containing natural or synthetic fibers, woven or non-woven fabrics, porous media. In a preferred embodiment first and second capillary medium are a single piece, for example shaft and screen are made of a sheet of card board or non-woven welded or laminated material, which is cheap and therefore suited for the production of a mass article. Shaft and screen are preferably rigid to maintain the shape of the transfer unit and its position with respect to the reservoir when introduced into the dispenser.
In a preferred embodiment of the invention the screen is permeable to air flow through the screen in a direction approximately normal to the plane of the screen. This can be achieved by a screen having one or more openings. In one preferred embodiment there are a plurality of xe2x80x9csmallxe2x80x9d openings, each with an area less than 5% of the total screen area, distributed preferably uniformly over the screen and result in openings in the screen totalling no more than 95%. By the screen material itself being capillary at least between the openings the liquid is distributed over the screen and around the openings where it evaporates. Additionally or alternatively, the openings or the whole screen area can be covered with another air permeable capillary medium, such as a gauze sheet or tissue paper, which additionally respectively solely receives and distributes the liquid. In this case there is not need for the openings being xe2x80x9csmallxe2x80x9d, i.e. one or more xe2x80x9cbiggerxe2x80x9d openings each with an area of equal to or greater than 5% of the total screen area can be used to transmit the air. To enhance evaporation, an externally generated air flow is advantageous but not essential.
The refill according to the invention comprises a reservoir containing the liquid, an outlet opening and a shaft receiving passage starting at the outlet opening and projecting inward. The shaft receiving passage is suitable for receiving the shaft of the transfer unit as described above. Preferably the receiving passage is dimensioned to tightly embrace the shaft, as this stabilizes the transfer unit and a capillary effect can be achieved between the shaft and the walls of the receiving passage enhancing the capillary action of the shaft itself. Another embodiment of the shaft may be envisaged where lower capillary action is required. This can be achieved through tapering of the shaft for the lower portion of ist length, such that it is not in intimate contact wiht the lower portion of the receiving passage. The refill and the shaft receiving passage may be moulded in one piece which can be produced at low cost. In a preferred embodiment the shaft receiving passage comprises a seal, e.g. a metal foil, plastic moulding, or any inpervious material that can be easily punctured isolating the liquid in the reservoir from the outside. Preferably, the seal is located at the bottom end of the passage and may be punctured by the shaft when fully introduced into the refill. A commercial embodiment of this could have the shaft partially introduced into the shaft receiving passage and the action of inserting the refill into the main unit causes the shaft to break the seal. To facilitate breaking the seal the shaft preferably comprises a cutting member at its bottom portion, e.g. a tip or a thorn or a knife-like element. Seal location at the bottom end of the passage is advantageous as the narrow passage protects the seal against accidental damage. The refill can thus be sold ready for use without an extra cover of the outlet opening, such as a lid, thus saving material, waste and manufacturing costs. Introduction of the shaft can be accomplished without spilling.
The transfer unit is preferably sold in a blister package containing one or more transfer units or a refill and an isolated unit insertable into the refill.
A coating of the lateral shaft faces respectively a layer around these faces impermeable to liquid is advantageous as it prevents softening of the shaft and stabilizes the shaft. Further, it enables the control of the dispensed amount as liquid flow can be stopped by tilting or turning the reservoir, thus preventing contact of the bottom portion with the liquid.